The purpose is to isolate and characterize enzymes involved in the biosynthesis of lactose which are UDP glucose Pyrophosphorylase, UDP-galactose-4-Epimerase, and Lactose Synthetase. Lactose synthetase requires two proteins for activity, a galactosyltransferase and alpha-lactalbumin. This protein-protein interaction is studied by kinetics and chemical modification techniques. The galactosyltransferase is also involved in the biosynthesis of glycoproteins. BIBLIOGRAPHIC REFERENCES: Magee, S.C., Geren, C.R. and Ebner, K.E. (1976) Plasmin and the Conversion of the Molecular Forms of Bovine Milk Galactosyltransferase, Biochim, Biophys. Acta 420, 187-194. Geren, C.R., Magee, S.C. and Ebner, K.E. (1976) Hydrophobic Chromatography of Galactosyltransferase, Arch. Biochem. Biophys. 172, 149-155.